Exodus 12:3-4

3Speak to all the congregation of Israel, saying: ‘On the tenth of this month every man shall take for himself a lamb, according to the house of his father, a lamb for a household.

4And if the household is too small for the lamb, let him and his neighbor next to his house take it according to the number of the persons; according to each man’s need you shall make your count for the lamb.